Pad with shallow cells for electrochemical mechanical processing

ABSTRACT

The present invention generally provides a polishing article that is easy to clean, reduces debris and by product accumulation and reduces amount of polishing solution needed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a processingapparatus for planarizing or polishing a substrate. More particularly,the invention relates to polishing pad design for planarizing orpolishing a semiconductor substrate by electrochemical mechanicalplanarization.

2. Description of the Related Art

In the fabrication of integrated circuits and other electronic deviceson substrates, multiple layers of conductive, semiconductive, anddielectric materials are deposited on or removed from a substrate, suchas a semi conductor substrate. As layers of materials are sequentiallydeposited and removed, the substrate may become non-planar and requireplanarization, in which previously deposited material is removed fromthe substrate to form a generally even, planar or level surface. Theprocess is useful in removing undesired surface topography and surfacedefects, such as rough surfaces, agglomerated materials, crystal latticedamage and scratches. The planarization process is also useful informing features on the substrate by removing excess deposited materialused to fill the features and to provide an even or level surface forsubsequent deposition and processing.

Electrochemical Mechanical Planarization (ECMP) is one exemplary processwhich is used to remove materials from the substrate. ECMP typicallyuses a pad having conductive properties and combines physical abrasionwith electrochemical activity that enhances the removal of materials.The pad is attached to an apparatus having a rotating platen assemblythat is adapted to couple the pad to a power source. The apparatus alsohas a substrate carrier, such as a polishing head, that is mounted on acarrier assembly above the pad that holds a substrate. The polishinghead places the substrate in contact with the pad and is adapted toprovide downward pressure, controllably urging the substrate against thepad. The pad is moved relative to the substrate by an external drivingforce and the polishing head typically moves relative to the moving pad.A chemical composition, such as an electrolyte, is typically provided tothe surface of the pad which enhances electrochemical activity betweenthe pad and the substrate. The ECMP apparatus may affect abrasive and/orpolishing activity from frictional movement while the electrolytecombined with the conductive properties of the pad selectively removesmaterial from the substrate.

Although ECMP has produced good results in recent years, there is anongoing effort to develop pads that improve polishing qualities, requireless conditioning, and consume less polishing solution. For example, aconductive polishing pad used in an ECMP process generally includes ananode and a cathode (or counter electrode) separated by an insulatinglayer and porous foam pad. The foam pad provides mechanical cushion forglobal flexibility. The insulating layer and porous foam pad are exposedto polishing solution and tend to trap debris and byproducts duringpolishing. The debris and byproducts may scratch the substrate surfaceif not removed. Generally, renewing the polishing solution and rinsingthe polishing pad may reduce the debris and byproducts. However, thefoam pad makes it difficult to rinse the polishing pad and addsconsumption of polishing solution.

Therefore, there exists a need in the art for a processing article orpad that is easy to clean and reduces amount of polishing solution used.

SUMMARY OF THE INVENTION

The present invention generally provides a polishing article that iseasy to clean, reduces debris and byproduct accumulation and reducesamount of polishing solution needed.

One embodiment of the present invention provides a pad assembly forprocessing a substrate comprising a first conductive layer having anupper surface adapted to contact the substrate, a second conductivelayer disposed below the first conductive layer with an insulative layertherebetween, and a compressive layer disposed below the secondconductive layer opposite the first conductive layer, wherein aplurality of recesses are formed above the second conductive layer.

Another embodiment of the present invention provides a pad assembly forprocessing a substrate comprising a first electrode, a compressive layerdisposed on one side of the first electrode, and a plurality of discretemembers coupled to the first electrode opposite the compressive layer,wherein the plurality of discrete members and the first electrode definea plurality of recesses configured to retain a processing solutiontherein, each of the plurality of discrete members comprises aconductive layer adapted to contact the substrate and an insulativelayer disposed between the first electrode and the conductive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the embodiments thereofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only typical embodimentsof this invention and are therefore not to be considered limiting of itsscope, for the invention may admit to other equally effectiveembodiments.

FIG. 1 schematically illustrates a sectional side view of an exemplaryECMP station.

FIG. 2A schematically illustrates a top view of a pad assembly inaccordance with one embodiment of the present invention.

FIG. 2B schematically illustrates an enlarged portion of a processingsurface of the pad assembly shown in FIG. 2A.

FIG. 3 schematically illustrates a sectional side view of a portion of apolishing assembly in accordance with one embodiment of the presentinvention.

FIG. 4 schematically illustrates a sectional side view of a portion of apolishing assembly in accordance with another embodiment of the presentinvention.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The words and phrases used in the present invention should be giventheir ordinary and customary meaning in the art by one skilled in theart unless otherwise further defined. The embodiments described hereinmay relate to removing material from a substrate, but may be equallyeffective for electroplating a substrate by adjusting the polarity of anelectrical source. Common reference numerals may be used in the Figures,where possible, to denote similar elements depicted in the Figures.

FIG. 1 schematically illustrates a sectional side view of an exemplaryECMP station 102. The ECMP station 102 comprises a carrier head assembly152 positioned over a platen assembly 230. The carrier head assembly 152generally comprises a drive system 202 coupled to a carrier head 186.The drive system 202 may be coupled to a controller that provides asignal to the drive system 202 for controlling the rotational speed anddirection of the carrier head 186.

A processing pad assembly 222 is disposed on the platen assembly 230.The processing pad assembly 222 is configured to receive an electricalbias to perform a plating process and/or an electrochemical mechanicalpolishing/planarizing process.

The drive system 202 generally provides at least a rotational motion tothe carrier head 186 and additionally may be actuated toward the ECMPstation 102 such that a device side 115 of the substrate 114 retained inthe carrier head 186, may be disposed against a processing surface 125of the pad assembly 222 during processing.

Typically, the substrate 114 and the processing pad assembly 222 arerotated relatively to one another in an ECMP process to remove materialfrom the device side 115 of the substrate 114. Depending on processparameters, the carrier head 186 is rotated at a rotational speedgreater than, less than, or equal to, the rotational speed of the platenassembly 230. The carrier head assembly 152 is also capable of remainingfixed and may move in a path indicated by arrow 107 during processing.The carrier head assembly 152 may also provide an orbital or a sweepingmotion across the processing surface 125 during processing.

In one embodiment, the processing pad assembly 222 may be adapted toreleasably couple to an upper surface 260 of the platen assembly 230.The pad assembly 222 may be bound to the upper surface 260 by the use ofpressure and/or temperature sensitive adhesives, allowing replacement ofthe pad assembly 222 by peeling the pad assembly from the upper surface260 and applying fresh adhesive prior to placement of a new pad assembly222. In another embodiment, the upper surface 260 of the platen assembly230, having the processing pad assembly 222 coupled thereto, may beadapted to releasably couple to the platen assembly 230 via fasteners,such as screws.

The platen assembly 230 is typically rotationally disposed on a base 108and is typically supported above the base 108 by a bearing 238 so thatthe platen assembly 230 may be rotated relative to the base 108. Theplaten assembly 230 may be fabricated from a rigid material, such as ametal or rigid plastic, and in one embodiment the platen assembly 230has an upper surface 260 that is fabricated from or coated with adielectric material, such as CPVC. The platen assembly 230 may have acircular, rectangular or other plane form and the upper surface 260 mayresemble that plane form.

An electrolyte 204 may be provided from the source 248, throughappropriate plumbing and controls, such as a conduit 241, to a nozzle255 above the processing pad assembly 222 of the ECMP station 102.Optionally, an enclosure 206 may be defined in the platen assembly 230for containing an electrolyte and facilitating ingress and egress of theelectrolyte to the pad assembly 222.

In the embodiment shown in FIG. 1, the electrolyte 204 is provided fromthe nozzle 255. The electrolyte 204 may form a bath that is bounded by aplaten lip 258 adapted to contain a suitable processing level of theelectrolyte 204 while rotating. Alternatively, the electrolyte 204 maybe provided by the nozzle 255 continuously or at intervals to maintain asuitable level of electrolyte in the processing pad assembly 222. Afterthe electrolyte 204 has reached its processing capacity and is ready forreplacement, the platen assembly 230 may be rotated at a higherrotational speed and the spent electrolyte 204 is released by the actionof centrifugal force over the platen lip 258. In another embodiment, theplaten assembly 230 is rotated at a higher rotational speed the spentelectrolyte is released through perforations in the platen lip 258 thatmay be opened and closed by an operator or controlled by rotationalspeed. Alternatively or additionally, the spent electrolyte may bereleased through at least one perforation performing as a drain formedthrough various layers of the pad assembly 222 and the platen assembly230.

The pad assembly 222 comprises a first conductive layer 211, a secondconductive layer 212, an insulative layer 214 disposed between the firstconductive layer 211 and the second conductive layer 212, and acompressive layer 216. In one embodiment, the pad assembly 222 maycomprise a pad base 210 on which the rest of the layers are stacked.

In one embodiment, the first conductive layer 211 and the insulativelayer 214 may form a plurality of posts or discrete members 205extending from the second conductive layer 212.

The discrete members 205 may include any geometrical shape, such asovals, rectangles, triangles, hexagons, octagons, or combinationsthereof. A processing surface 125 is generally defined by an upperportion of each of the plurality of discrete members 205, and theplurality of apertures 209. The plurality of apertures 209 are generallydefined by the open areas between the plurality of discrete members 205.

Each of the plurality of apertures 209 defines a functional cell 207which is configured to receive an electrolyte. Each of the functionalcells 207 are adapted to perform as an electrochemical cell when theelectrolyte 204 is provided to the pad assembly 222, and a differentialelectrical bias is applied to the first conductive layer 211 and thesecond conductive layer 212. The second conductive layer 212 may have acontinuous body, for example a whole disk, preventing the electrolytefrom contacting the compressive layer 216.

In one embodiment, the plurality of apertures 209, define an open areabetween about 10 percent to about 90 percent, for example, between about20 percent to about 70 percent.

The compressive layer 216 may be made of a soft material that isconfigured to provide compressibility to the pad assembly 222.

FIG. 2A schematically illustrates a top view of the pad assembly 222 Thepad assembly 222 is exemplarily shown here having a circular processingsurface 125. The processing surface 125 includes the plurality ofdiscrete members 205 adjacent the plurality of apertures 209. Also shownis a first connector 264 coupled to the first conductive layer 211 and asecond connector 262 coupled to the second conductive layer 212. Thefirst and second connectors 264, 262 include a hole 261, 263respectively, for coupling to a mating electrical connection on theplaten assembly 230 and may also facilitate coupling of the pad assembly222 to the platen assembly 230.

FIG. 2B schematically illustrates an enlarged portion of the processingsurface 125 of the pad assembly 222 shown in FIG. 2A. The plurality ofapertures 209 are interspersed within the plurality of discrete members205. Each of the plurality of apertures 209 are surrounded by aplurality of channels 252. In one embodiment, the plurality of channels252 may be formed in the first conductive layer 211 by such methods asembossing or compression molding.

FIG. 3 schematically illustrates a sectional side view of a portion of apad assembly 322 in accordance with one embodiment of the presentinvention.

The pad assembly 322 comprises a first conductive layer 311, a secondconductive layer 312, an insulative layer 314 disposed between the firstconductive layer 311 and the second conductive layer 312. The insulativelayer 314 is configured to electrically isolate the first conductivelayer 311 from the second conductive layer 312. The pad assembly 322further comprises a compressive layer 316 disposed on one side of thesecond conductive layer 312 opposing the insulative layer 314. The padassembly 322 further comprises a pad base 310 on which the rest of thelayers are stacked.

In one embodiment, the first conductive layer 311 and the insulativelayer 314 may form a plurality of discrete members 305 extending fromthe second conductive layer 312. The plurality of discrete members 305may include any geometrical shape, such as ovals, rectangles, triangles,hexagons, octagons, or combinations thereof.

A plurality of apertures 309 are formed between the plurality ofdiscrete members 305. The plurality of apertures 309 are generallydefined by the open areas between the plurality of discrete members 305.The plurality of apertures 309 are connected to one another and areconfigured to retain an electrolyte therein. A processing surface 325 isgenerally defined by an upper portion of each of the discrete members305.

The first conductive layer 311 and second conductive layer 312 may beconnected to a power source 320 during processing. The electrolyte, whenretained in the plurality of apertures 309, may form an electrochemicalcell with the first and second conductive layers 311, 312 to remove ordeposit a conductive material from or onto a surface in contact with theprocess surface 325.

The second conductive layer 312 is stacked on the compressive layer 316which is stacked on a pad base 310. The compressive layer 316 isconfigured to provide compressibility to the pad assembly 322. Thecompressive layer 316 is not in fluid communication with the pluralityof apertures 309, therefore, not in contact with the electrolyte duringprocessing. The pad base 310 is configured to support the pad assembly322.

When used in an electrochemical processing, such as electrochemicalmechanical polishing or electroplating, the pad assembly 322 presentsseveral advantages over the state of the art pad assemblies.

First, the pad assembly 322 has a reduced resistance between electrodes,i.e. between the first conductive layer 311 and the second conductivelayer 312. This may be a result of the second conductive layer 312 beinga whole piece instead of being distributed in a plurality of discretemembers. Additionally, less electrolyte is disposed between the firstand second conductive layers 311, 312 because height of the plurality ofapertures 309 is reduced. In this embodiment, only thickness of thefirst conductive layer 311 and the insulative layer 314 contributes tothe height of the plurality of apertures 309.

Second, volume of electrolyte used during processing may be reduced.Again, this may be contributed to the reduced height of the plurality ofapertures 309. The reduced volume of electrolyte used makes it possibleto replace the electrolyte and rinse the pad assembly more often withoutincreasing product costs and reducing system throughput. In oneembodiment, the electrolyte may be replaced for every substrate duringpolishing.

Third, defects on substrates being processed may be reduced becausethere is less room for storing particles and by products because lesslayers are exposed to the electrolyte during processing. Particularly,porous layers, such as the compressive layer 316, are not in fluidcommunication with the electrolyte.

Fourth, chemical decomposition is also reduced because less layers areexposed to the electrolyte during processing. Particularly, thecompressive layer 316, which is more prone to decomposition, is not incontact with the electrolyte.

The first conductive layer 311 may comprise a conductive polymermaterial. In one embodiment, the first conductive layer 311 comprises aconventional polishing material, such as polymer based pad materialscompatible with the process chemistry, examples of which includepolyurethane, polycarbonate, fluoropolymers,polytetraflouroethylene(PTFE), polytetraflouroacrylate (PTFA),polyphenylene sulfide (PPS), or combinations thereof. The conventionalpolishing material may be coated, doped, or impregnated with a processcompatible conductive material and/or particles. Alternatively, thefirst conductive layer 311 may be a conductive polymer, such as aconductive filler material disposed in a conductive polymer matrix, suchas fine tin particles in a polyurethane binder, or a conductive fabric,such as carbon fibers in a polyurethane binder.

In one embodiment, the first conductive layer 311 comprises removalparticles adapted to facilitate material removal from the device side ofthe substrate. In one embodiment, the removal particles are conductiveparticles, such as particles of tin, copper, nickel, silver, gold, orcombinations thereof, in a conductive polymer matrix. In anotherembodiment, the removal particles are abrasive particles, such asaluminum, ceria, oxides thereof and derivatives thereof, andcombinations thereof, in a conductive polymer matrix. In yet anotherembodiment, the removal particles are a combination of abrasive andconductive particles as described herein and are interspersed within thefirst conductive layer 311. The first conductive layer 311 may furtherinclude a chamfer, a bevel, a square groove, or combinations thereof,which is adapted to facilitate electrolyte and polishing byproducttransportation.

The second conductive layer 312 may be fabricated from a conductivematerial, such as stainless steel, aluminum, gold, silver, copper, tin,nickel, among others. For example, the second conductive layer 312 maybe a metal foil, a mesh made of metal wire or metal-coated wire, or alaminated metal layer on a polymer material compatible with theelectrolyte, such as a polyimide, polyester, flouroethylene,polypropylene, or polyethylene sheet. In one embodiment, the secondconductive layer 312 is configured to provide conformity and sufficientstiffness to allow the pad assembly to remain substantially flat alone,or in combination with the pad base 310. In one embodiment, the secondconductive layer 312 comprises a copper mesh.

The insulative layer 314 may be fabricated from polymeric materials,such as polyurethane and polyurethane mixed with fillers, polycarbonate,polyphenylene sulfide (PPS), ethylene-propylene-diene-methylene (EPDM),Teflon™ polymers, or combinations thereof, and other polishing materialsused in polishing substrate surfaces, such as open or closed-cell foamedpolymers, elastomers, felt, impregnated felt, plastics, and likematerials compatible with the processing chemistries.

The compressive layer 316 may be made of a polymer material, such as anopen cell foamed polymers, closed cell foamed polymers, a MYLAR®material, heat activated adhesives, or combinations thereof. In oneembodiment, the compressive layer 316 may have a hardness of about 20Shore A to about 90 Shore A. In one embodiment, the foam layer 316comprises open cell foam, such as a urethane material sold under thetrade name PORON®, which is available from the Rogers Corporation. Inone embodiment, the foam layer 316 comprises a material under the tradename PORON® 30 or PORON® 35.

In one embodiment, binding layers 321 a-d may be used in between theabove described layers. The binding layers 321 a-d may be made of anadhesive that is compatible with process chemistry, such as heat and/orpressure sensitive adhesives known in the art.

FIG. 4 schematically illustrates a sectional side view of a portion of apad assembly 422 in accordance with another embodiment of the presentinvention.

The pad assembly 422 is similar to the pad assembly 322 illustrated inFIG. 3 except that the pad assembly 422 comprises a conductive carrierlayer 415 between the first conductive layer 311 and the insulativelayer 314. A plurality of discrete members 405 may extend from thesecond conductive layer 312. A plurality of apertures 409 may be formedin the space separating the plurality of the discrete members 405. Aprocessing surface 425 is generally defined by an upper portion of eachof the discrete members 405.

The conductive carrier layer 415 is configured to improve uniformityacross a substrate being processed. In one embodiment, the conductivecarrier layer 415 comprises a conductive material, such as stainlesssteel, aluminum, gold, silver, copper, tin, nickel, among others. Forexample, the conductive carrier layer 415 may be a metal foil, a meshmade of metal wire or metal coated wire, metal coated fabric, or alaminated metal layer on a polymer material compatible with theelectrolyte used in processing, such as a polyimide, polyester,flouroethylene, polypropylenen, or polyethylene sheet.

While the foregoing is directed to the illustrative embodiment of thepresent invention, other and further embodiments of the invention may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A pad assembly for processing. a substrate, comprising: a first conductive layer having an upper surface adapted to contact the substrate; a second conductive layer disposed below the first conductive layer with an insulative layer therebetween; and a compressive layer disposed below the second conductive layer opposite the first conductive layer, wherein a plurality of recesses are formed above the second conductive layer.
 2. The pad assembly of claim 1, further comprising a conductive carrier coupled to and disposed below the first conductive layer.
 3. The pad assembly of claim 2, wherein the conductive carrier is made of a fabric coated with conductive material.
 4. The pad assembly of claim 1, wherein the first conductive layer comprises a plurality of discrete members separated by the plurality of recesses, and the second conductive layer defines a bottom wall of the plurality of recesses.
 5. The pad assembly of claim 4, wherein the second conductive layer has a continuous body.
 6. The pad assembly of claim 4, wherein compressive layer is not in fluid communication with the plurality of recesses.
 7. The pad assembly of claim 1, wherein the plurality of recesses define an open area of between about 10 to about 90 percent of the pad assembly.
 8. The pad assembly of claim 1, further comprising a pad base disposed below the compressive layer.
 9. The pad assembly of claim 1, wherein the first conductive layer comprises a plurality of removal particles.
 10. The pad assembly of claim 9, wherein the plurality of removal particles are abrasive particles.
 11. The pad assembly of claim 1, further comprises binding layers between the first conductive layer and the insulative layer, between the insulative layer and the second conductive layer, and between the second conductive layer and the compressive layer.
 12. The pad assembly of claim 1, wherein the second conductive layer comprises a copper mesh.
 13. A pad assembly for processing a substrate, comprising: a first electrode; a compressive layer disposed on one side of the first electrode; and a plurality of discrete members coupled to the first electrode opposite the compressive layer, wherein the plurality of discrete members and the first electrode define a plurality of recesses configured to retain a processing solution therein, each of the plurality of discrete members comprises a conductive layer adapted to contact the substrate and an insulative layer disposed between the first electrode and the conductive layer.
 14. The pad assembly of claim 13, wherein the conductive layer comprises: a conductive composite having a processing surface configured to contact the substrate; and a conductive carrier coupled to the conductive composite opposite the processing surface.
 15. The pad assembly of claim 14, wherein the conductive carrier comprises a fabric coated with a conductive material.
 16. The pad assembly of claim 13, wherein the conductive layer comprises a plurality of conductive particles, a conductive foil or a conductive foam.
 17. The pad assembly of claim 13, wherein the conductive layer comprises abrasive particles.
 18. The pad assembly of claim 13, further comprising a pad base coupled to the compressive layer.
 19. The pad assembly of claim 13, wherein the compressive layer is not in fluid communication with the plurality of recesses.
 20. The pad assembly of claim 13, wherein the first electrode comprises a copper mesh or copper mesh. 